Thermoplastic containers manufactured by extrusion blow molding apparatus

ABSTRACT

Extrusion blow molding apparatus ( 10 ) having a blow mold ( 12 ), a neck mold ( 14 ) positioned above the blow mold and an anvil ( 30 ) positioned in an outwardly facing cavity ( 32 ) of the neck mold. A container (C) is produced in the molding apparatus from a parison of a heated thermoplastic material by introducing pressurized blowing fluid into the container being formed by way of a blow pin assembly ( 16 ) that is reciprocable relative to the blow mold. The blow pin assembly has an inner tubular member ( 20 ) with a free end that is within the container during blowing, and an outer tubular member ( 22 ) that surrounds the inner tubular member and defines an annulus therewith for withdrawing spent blowing fluid from the container. The outer tubular member has radial ports ( 24 ) for directing spent blowing fluid against a moil (M) being formed at a rim (R) of a finish (F) of the container. A restricted outlet from the finish of the container is obtained by providing the anvil with an inwardly and downwardly directed nose portion ( 34 ) to form a restricted annular portion (P) in the finish at a location below the rim.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a division of co-pending U.S. patentapplication Ser. No. 09/288,208, which was filed on Apr. 18, 1999.

FIELD OF THE INVENTION

[0002] This invention relates to an improved container manufactured bythe extrusion blow molding process, a process that is occasionallyreferred to as the “shuttle” blow molding process. More particularly,this invention relates to a container of the foregoing character with anintegral restricted outlet.

BACKGROUND OF THE INVENTION

[0003] In the manufacture of thermoplastic containers by the shuttleblow molding process, the threaded or otherwise configured closurereceiving neck portion of the container, which is commonly referred toas the “finish” of the container, is formed by a neck mold that ispositioned against an outermost end surface of a body mold cavity inwhich the body portion of the container is blown from a previouslyextruded form or parison of the container. The blowing of the containeris done by air or another gas that is introduced into the parison withinthe mold cavity by a blow pin that extends through the neck mold intothe parison within the body mold. The blow pin reciprocates with respectto the neck mold and body mold, and an anvil of a hard material ispositioned within an open-ended cavity on the outermost surface of theneck mold to prevent impact damage to the neck mold as the blow pinreciprocates with respect to the neck mold.

[0004] In the manufacture of thermoplastic containers by the extrusionblow molding process, heretofore it has been very difficult to produce acontainer with a smaller internal control diameter at or near the top ofits finish, the “C” dimension in industry nomenclature, than the minimuminternal diameter at or near the bottom of the finish, the “I” diameterin industry nomenclature. However, for proper dispensing of the packagedproduct, when the packaged product is a liquid, it is often importantthat the size of the opening at the “C” dimension be substantiallysmaller than the “I” dimension. Heretofore, this has usually beenaccomplished by inserting a separate annular fitment in the outlet ofthe container finish. This added element, and the assembly step involvedin its insertion in a container, however, add to the expense involved inthe manufacture of restricted outlet liquid containers by the extrusionblow molding process.

[0005] Another problem encountered in the manufacture of thermoplasticcontainers by the extrusion blow molding process, according to prior arttechniques, relates to dimensional variations in the rims of suchcontainers resulting from the time required to properly cool the portionof the container to be removed from the rim, often called a “moil,” atthe conclusion of the blow molding process.

[0006] Another problem encountered in the manufacture of thermoplasticcontainers by the extrusion blow molding process, according to prior arttechniques, relates to the removal of the moils from the containers atthe conclusion of the molding process, especially containers producedwith a restricted outlet. Heretofore, stripper plates, which areconventionally used to remove moils from other types of extrusion blowmolded containers, were not effective in removing moils from restrictedoutlet containers of such type, and such moils often disengaged from thecontainers in an uncontrolled manner upon impact of the containers witha removal conveyor.

BRIEF DESCRIPTION OF THE INVENTION

[0007] The aforesaid and other problems heretofore associated with themanufacture of containers by the extrusion blow molding process aresolved by the apparatus of the present invention in which the containeris provided with a “C” dimension that is substantially smaller than its“I” dimension, to eliminate the need for inserting a separate fitmentinto the container to be able to properly control the rate of flow ofliquid from the container, and this is done by providing the anvil usedin such process with an annular, transversely extending partition at anelevation that will occur within the finish of the container, near butbelow the rim of the container. Such anvil partition will then serve tomold a restricted diameter annular partition within the container neckin addition to performing its historical function of preventing neckdamage to the adjacent neck mold of the apparatus, and the restricteddiameter annular partition thereby formed within the container finishwill be an integral part of a single piece container and finish.

[0008] The extrusion blow molding apparatus of the present inventionalso provides containers with more precisely defined finishes by the useof a blow pin assembly that exhausts spent cooling air in an annulusthat surrounds a cooling air inlet tube, and the exhausted spent coolingair is exhausted from the annulus of the blow pin assembly against themoil portion of the container being molded, that is, the annular portionof the container that projects outwardly from the rim at the finish ofthe container, such moil portion normally being trimmed from thecontainer during or after its discharge from the mold. This spentcooling air discharge technique serves to accelerate the cooling of themoil, and to a lesser extent the cooling of the finish itself, and thisacceleration of the cooling rates in the region of the finish of thecontainer will help to reduce the distortion of the container finishthat occurs when finish cooling occurs more slowly.

[0009] The extrusion blow molding apparatus of the present inventionalso provides for the stripping, or removal, of the moil section of ablow molded container with a restricted outlet before the container isremoved from the mold, and therefore before the container is impactedagainst a removable conveyer, an action that heretofore was notconsistently possible. According to the present invention, at theconclusion of the molding cycle the mold opens and the blow pin assemblyis retracted relative to the mold. The shoulder of a tube of the blowpin assembly is stopped by a pair of tube drop rods, and the stem of theblow pin assembly continues to rise. The moil of the container, nowdetached or partly detached from the container finish because it engagesthe exterior of the blow pin assembly, is held up by a stripper doughnutinsert. The stem of the blow pin assembly continues to rise through thestripper doughnut insert, which causes the moil to disengage from theblow pin assembly and fall to a conveyer below the mold.

[0010] Accordingly, it is an object of the present invention to providean improved thermoplastic container. More particularly, it is the objectof the present invention to provide an improved container with arestricted outlet.

[0011] For a further understanding of the present invention and theobjects thereof, attention is directed to the drawing and the followingbrief description thereof, to the detailed description of the preferredembodiment and to the appended claims.

BRIEF DESCRIPTION OF THE DRAWING

[0012]FIG. 1 is a fragmentary elevational view, partly in cross-section,of apparatus for blow molding a container according to the preferredembodiment of the present invention from a thermoplastic materialaccording to the extrusion blow molding process;

[0013]FIG. 2 is a fragmentary view, at an enlarged scale, of a portionof the apparatus shown in FIG. 1;

[0014]FIG. 3 is a fragmentary elevational view, at a reduced scale, of aportion of the apparatus of FIGS. 1 and 2 showing a step in theextrusion blow molding process occurring after the step illustrated inFIGS. 1 and 2;

[0015]FIG. 4 is a view similar to FIG. 3 showing a subsequent step inthe manufacture of containers according to the preferred embodiment ofthe present invention;

[0016]FIG. 5 is a view similar to FIGS. 3 and 4 showing anothersubsequent step in the manufacture of containers according to theextrusion blow molding process of the present invention; and

[0017]FIG. 6 is a perspective view showing a detail of the apparatus ofFIGS. I and 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] A container C according to the present invention is shown inFIGS. 1 and 2 being molded in blow molding apparatus according to thepresent invention, such apparatus being generally identified byreference numeral 10. As shown in FIGS. 1 and 2, the blow moldingapparatus 10 is made up of a blow mold 12 in which a body portion of thecontainer C is formed by blowing, and a neck mold 14 in which a threadedor otherwise configured closure receiving finish portion F of thecontainer C is formed. In that regard, the blow mold 12 is made up ofopposed, semi-cylindrical mold halves, which, when joined end-to-end,define a cavity corresponding in configuration to the exterior of thebody portion of the container C; likewise, the neck mold 14 is made upof an opposed, like pair of mold halves which, when joined end-to-end,define a cavity whose configuration corresponds to the exterior of thefinish F of the container C.

[0019] In the manufacture of containers by an extrusion blow moldingprocess, in which the blow molding apparatus 10 is adapted to be used,containers are produced from extruded forms, often called parisons,which are produced elsewhere in an extrusion blow molding machine andare then transferred to a blow molding station for blowing intocontainers. In any event, the containers C are blown from extrudedparisons that are extruded from a melt of a thermoplastic material, suchas polypropylene or high density polyethylene, as is known in the art,and the blow molding process occurs while such thermoplastic material isat an elevated temperature.

[0020] The container C is blown in the blow molding apparatus by blowingair or other gaseous medium that is introduced in the container C whilethe container C is in the blow mold 12 of the blow molding apparatus 10by air that is introduced through a blow pin assembly, which isgenerally indicated by reference numeral 16. The blow pin assembly 16,which is reciprocable relative to the blow mold 12, receives blowing airthrough an inlet line 18, and the blowing air, which is cooler than theparison to be blown into the container C, passes from the air inlet line18 into the interior of the parison to be blown into a container in theblow mold 12 through an air introduction tube 20. Spent blowing air fromthe container being blown in the blow mold 12 is withdrawn therefrom inan annulus that is defined by the exterior of the air introduction tube20 and the interior of an annular tube 22, whose free end terminateswithin a container C short of the termination of a free end of the airintroduction tube 20. Radial exhaust ports 24 are formed in the annulartube 22 at the location of an annular moil portion M that is formed at arim R of the annular finish portion F of the container C, and spentblowing air from the annular tube 22, which is still cooler than themoil M of the container C, is directed against the moil M through theexhaust ports 24 and through radially aligned ports 26 in an annularmember 28 that supports an exterior free end portion of the annular tube22. This cooling of the moil M, which results in cooling of the finish Fto a lesser extent, results in less thermal distortion of the finish Fthan would otherwise occur in an arrangement where cooling proceededmore slowly, and results in a more precisely defined finish F because ofsuch accelerated cooling.

[0021] Because of the reciprocation of the blow pin assembly relative tothe blow mold 12, as heretofore described, impact loads would be borneby the neck mold 14, but for the presence of an anvil 30 of a hardmaterial that is made up of opposed, semi-cylindrical elements joinedend-to-end to form an annular opening. The anvil 30 is placed againstthe exterior of the neck mold 14, specifically, in an open cavity 32thereof. In the present case, the anvil 30 has an inwardly anddownwardly projecting nose portion 34 that projects into the finish F ofthe container C to form, with the exterior of the blow pin assembly 16,a transversely extending annular partition P integrally with thecontainer C and at a location slightly below the rim of the finish F.The inside diameter of the partition P, then, becomes the “C” dimensionof the container finish F, and the “C” dimension can be substantiallysmaller than the “I” dimension of the finish F, which will occur nearthe juncture of the finish F and a shoulder portion S of the containerC. With such a restricted “C” dimension, it becomes unnecessary toinsert a separate fitment into the outlet of the finish F to reduce therate at which liquid or other product packaged in the container C can bewithdrawn therefrom.

[0022] At the conclusion of the molding of the container C in the blowmolding apparatus 10, the neck mold 14, with the anvil 30, is removedform the blow molding apparatus 10, and the blow pin assembly 16 beginsto be retracted from the blow molding apparatus 10 relative to the blowmold 12 and to fixed support structure 36. This has the effect oflifting the container C out of the blow mold 12 by virtue of bondingbetween the blow pin assembly 16 and the thermoplastic material in thecontainer C, and specifically between the blow pin assembly 16 and thethermoplastic material in the moil M of the container C. This motioncontinues until the shoulder S of the container C engages the free endsof a pair of downwardly depending drop rods 38 that depend from a donutinsert 42 of stripper plate 40, which is releasably secured to thesupport structure 36, the releasable connection between the donut insert42 and the support structure 36 permitting the substitution of adifferent donut insert 42, with drop rods 38 that depend a differentdistance therefrom, as required to process containers C of a differentconfiguration. This is the condition depicted in FIG. 3.

[0023] As is shown in FIG. 4, the blow pin assembly 16 continues to bewithdrawn relative to the blow mold 12 and relative to the supportstructure 36. However, the container C is no longer free to moverelative to the blow mold 12 because of the engagement of the shoulder Sof the container C by the drop rods 38. Nevertheless, the continuedretraction of the blow pin assembly 16 will cause the moil M of thecontainer C to separate from the finish F of the container C because ofthe bonding of the interior of the moil M to the exterior of the blowpin assembly 16, and the moil M will thereby be separated from thecontainer C before the container C is withdrawn from the mold 12. Themoil M can then be disposed of at a location away from the mold 12, andno separate moil removal step need be performed on the container C afterits removal from the mold 12, the removal of the moil M from the blowpin assembly 16 being shown in FIG. 5.

[0024] Although the best mode contemplated by the inventor for carryingout the present invention as of the effective filing date hereof hasbeen shown and described herein, it will be apparent to those skilled inthe art that suitable modificafions, variations and equivalents may bemade without departing from the scope of the invention, such scope beinglimited solely by the terms of the following claims and the legalequivalents thereof.

What is claimed is:
 1. A container having a body portion and a finishportion formed integrally with said body portion, said container beingformed from an extruded parison of a thermoplastic material in blowmolding apparatus in which said body portion is formed from a portion ofthe parison in a blow mold of the blow mold apparatus and the finish isformed from another portion of the parison in a neck mold, said finishportion having an annular partition extending across said finish portionat a location positioned within said finish portion at an elevationbelow a rim of said finish portion, said annular partition having aninternal diameter that is substantially smaller than any other internaldiameter of said finish portion
 2. A container according to claim 1 inwhich said blow molding apparatus is apparatus of the extrusion blowmolding type.
 3. A container according to claim 2 in which the containeris produced from a melt of polypropylene or high density polyethylene.4. A container according to claim 1 wherein the internal diameter ofsaid annular partition is the “C” dimension of the finish portion of thecontainer.